Tuning CH4 Productivity from Visible Light-Driven Gas-Phase CO2 Photocatalytic Reduction on Doped G-C3n4/tio2 Heterojunctions

Herein, visible light-driven gas-phase photocatalytic CO2 reduction into CH4 is tuned by designing optimized three-component Au/doped C3N4/TiO2 composite photocatalysts. The key point strategy consists in the formation of high-quality C3N4/TiO2 heterojunction by associating low containing doped graphitic carbon nitride to commercially available TiO2 UV-100. Those heterojunctions result in both visible light sensitization and increased charge-carrier separation. Further deposition of small Au nanoparticles (approximate to 3nm), quite exclusively onto TiO2 surfaces, mainly acts as electron trapping/cocatalytic functions without excluding surface plasmonic effects. The resulting doped g-C3N4 material exhibits enhanced visible light harvesting properties, especially in the case of C-doping. In addition, it is assumed that B- and C-C3N4 doping, leading to a more or less lower conduction band position, is the impacting factor toward total CH4 selectivity achievement. The (0.77wt%)Au/(0.59wt%)C-C3N4/TiO2 composite photocatalyst, exhibiting the best compromise between the various impacting factors, leads to a continuous productivity rate of CH4 of 8.5 mu mol h(-1)g(-1) under visible light irradiation over at least 10h. To the best of knowledge, this level of performance is unprecedented under continuous gas-phase flowing CO2 in the presence of water as reducing agent, without addition of any sacrificial agent.